Patients.—All patients were randomly selected. For coronary angiography, 533 patients in Canada and 1333 patients in New York were selected; for CABG, 556 patients in Canada and 1336 patients in New York were selected.

Main Outcome Measures.—Percentage of patients in each country who had coronary angiography or CABG for necessary, appropriate, uncertain, or inappropriate indications as rated by criteria developed separately in each country and the complications of those procedures.

Results.—For coronary angiography, 9% of Canadian cases and 10% of New York cases were rated inappropriate using Canadian criteria compared with 5% and 4%, respectively, using US criteria. For CABG, 4% of Canadian cases and 6% of New York cases were rated inappropriate by Canadian criteria compared with 3% and 2%, respectively, using US criteria. A lower proportion of procedures were performed on persons aged 75 years or older in Canada than in New York for both coronary angiography (5% vs 11%; P<.001) and CABG (6% vs 14%; P<.001). Women were also represented in lower proportions among angiography cases in Canada than in New York (28% vs 35%; P=.023). Canadian patients with left main coronary disease waited significantly longer between angiography and CABG than did New York patients (P<.0001).

Conclusions.—Rates of inappropriate use of cardiac procedures were low in Canada and New York, which suggests that the regionalization of cardiac procedures that characterizes both health care systems contributes to better clinical decision making. Differences in the use of cardiac procedures among the elderly in the two countries merits further comparative examination.(JAMA. 1994;272:934-940)